Page History

public interface StreamOperator<OUT> extends CheckpointListener, KeyContext, Serializable {

    ....

    /**
     * This method is called at the end of data processing.
     *
     * <p>The method is expected to flush all remaining buffered data. Exceptions during this
     * flushing of buffered should be propagated, in order to cause the operation to be recognized
     * as failed, because the last data items are not processed properly.
     *
     * <p><b>After this method is called, no more records can be produced for the downstream operators.</b>
     *
     * <p><b>NOTE:</b>This method does not need to close any resources. You should release external
     * resources in the {@link #close()} method.
     *
     * @throws java.lang.Exception An exception in this method causes the operator to fail.
     */
    void finish() throws Exception;

    /**
     * This method is called at the very end of the operator's life, both in the case of a
     * successful completion of the operation, and in the case of a failure and canceling.
     *
     * <p>This method is expected to make a thorough effort to release all resources that the
     * operator has acquired.
     *
     * <p><b>NOTE:</b>It should not emit any records! If you need to emit records at the end of
     * processing, do so in the {@link #finish()} method.
     */
    void close() throws Exception;

    ...

}